Blasting explosive cartridge



July 28, .1936. A. G. WHITE BLASTING EXPLOSIVE CARTRIDGE Filed Jan. 10, 1934 gwuc/nm Alb E PT Er ravine Whfie Patented July 28, v 1936 UNITED STATES,

BLASTING EXPLOSIVE CARTRIDGE Albert Greville White, Saltcoats, Scotland, as-

signor to Imperial Chemical Industries Limited, a corporation of Great Britain Application January 10, 1934, Serial No. 706,143

In Great Britain January 10, 1933 10 Claims.

This invention relates to the manufacture of blasting explosive cartridges, more particularly those intended for use infiery mines, of the type in whichthe cartridge is made up of two distinct 5 parts, namely, an inner core of explosive and an outer annular sheath or jacket in which cooling agents are provided in order to reduce the tendency of the explosive to cause ignitions when used in fiery mines. The cooling agents which 10 have hitherto been proposed for use in this mannerv are such that they add little or nothing to the power of the explosive.

I have now discovered that when power producing salts especially ammonium nitrate, are

15 utilized in conjunction with suitable cooling agents in the outer sheath or jacket to a blasting explosive, the said power producing salts not only assist materially in reducing the tendency of the explosive to ignite firedamp, but also add notably 20 to the power produced.

The single figure of the drawing is a perspective view of a blastingcartridge sheathed in accordance with my invention. According to my invention in a cartridge the type described the jacket or sheath extends over substantially the whole length of the core and, if desired, around one orboth ends thereof, and comprises a mixture containing one or more cooling salts and one or more power producing 30 salts especially ammonium nitrate. The mixture may optionally contain minor proportions of sensitizing explosives such as nitroglycerine, trinitrotoluene, and/or a small amount of oxidizable carbonaceous material, for instance, wax.

I 35 The said mixture is hereinafter referred to as the cooling mixture, as distinct from the explosive mixture which forms the inner core of the cartridge. It is to be understood that the word cartridge is used above to designate only the 40 ultimate form in which the explosive appears, and that the explosive may be made into the form of a cartridge by the operation of filling it in granular or powder form into a preformed sheath of the cooling mixture. 45 The cooling agents may be any of the salts commonly employed as cooling agents in connection with blasting explosives, which are liquefied, volatilized, or decomposed with absorption of heat at the time of the explosion. I prefer to use inert salts such as the halides of the alkali metals, or salts, such as calcium carbonate, which give inert gases 'on decomposition. Alternatively, or in addition, I may use as cooling salts one "r more of those salts which; apart from 5 their cooling or safety characteristics, function to some extent as power producing salts. As examples of this class of salt may be mentioned the alkali nitrates, e. g. sodium nitrate. As the power producing salt I prefer to use ammonium nitrate, although this material may be substi- 5 tuted by ammonium perchlorate, or the chlorates or perchloratesof the alkali metals.

It will be understood that the constituents of the cooling mixture are so chosen that the mixture is not. chemically unstable at ordinary temperatures. In mixtures containing oxidizing salts the proportion of carbonaceous matter should be kept to aminimum, and when appreciable amounts of carbonaceous matter are present a comparatively high proportion of cooling salts should be added.

In putting my invention into effect, I may, for example, form a sheath or cup by casting the cooling mixture with or without a small proportion of water in a mould, into which sheath or cup, when cold, the explosive may be loaded. The core explosive may be introduced by pressing it in loose or in gelatinous form into the sheath or cup, or by slipping a previously formed cylinder of the core explosive into the sheath or cup, as is most convenient depending on the nature and consistency of the type of explosive to be used. Another method is to take a previously formed cylinder of the explosive, which may conveniently be wrapped in paper, and pro- 3g vide this with a sheath of the cooling mixture by forming a coating around it, but care must of course be taken to avoid the use of unduly high temperatures in the forming operation. Still another method is to form an annular space of the required width by means of cylinders of paper, metal foil, regenerated cellulose, or other suitable thin sheet materials, suitably backed by supporting cylinders throughout the filling operation. The cooling mixture is introduced into the annular space in compact form, e. g. by casting with or without a proportion of water, or by tamping, and the lower ends of the cylinders may, if desired, be folded over to form a cup. The supports are then removed and the explosize is loaded into the tube or cup without removing the cylinders of paper or other material. The outer wrapping is preferably waxed.

In ordinary circumstances I find that the sheath or jacket should be about 3 to 6 mm. in thickness throughout the length of the explosive cartridge. It is to be understood that greater or smaller thicknesses may be employed for particular purposes or for cartridges of unusual size or unusual explosive materials. When it is de- "while the addition of power producing salts to the cooling salts renders the cartridges more efli'cient in use. As compared with explosive cartridges which are not provided with a jacket containing cooling salts, but in which the cool-' ing salts are incorporated with the explosive mixture, my improved cartridges have the advantage that the inner core may be made to explode at a higher temperature than would be permissible in the case of safety explosives of the usual type, thus combining good propagation and sensitiveness with a high degree. of safety.

Example 1 A 1%" diameter cylinder of Polar Viking blasting explosive (British Home Omce permitted list) wrapped in waxed paper is placed centrally in a paper cylinder of about 10 mm. greater diameter and somewhat greater length, one end of which has been closed. The space between the wrapped cartridge and the paper cylinder is then filled up with a mixture'of pulverized ammonium nitrate and pulverized common salt in equal proportions, taking care that the filling is at least moderately even. The top of the paper .cylinder is then folded in to form an enclosed carton. Cartridges of this type may be used when it is desired to fire several cartridges in file.

Example 2 A 1%," diameter cylinder of Polar Viking blasting explosive (British Home Othce permitted list), wrapped in waxed paper, is placed centrally in a paper cylinder of about 10 mm. greater diameter and somewhat greater length, one end of which has been closed and provided with a 10 mm. layer of a cooling mixture consisting of ammonium perchlorate, sodium nitrate and sodium chloride. The space between the wrapped cartridge and the paper cylinder is then filled up with moderately tamped cooling mixture of the same composition, care being taken that the filling is at least moderately even. The top of the paper is then folded in toenclose the cartridge. This may be used for blasting where only a single cartridge is required in the borehole, or at' the most two, in which case the two cartridges would be arranged with the ends not provided with cooling -mixture towards one another.

If the end thickness of the cooling mixture is omitted, the cartridges may be used when it is desired to fire several cartridges in file.

Example 3 A cooling mixture consisting of "10 parts by weight of ammonium nitrate, 10 parts of sodium chloride, and 20 parts of ammonium dihydrogen phosphate is fused and cast into the annular space between two paper cylinders, leaving sufficient paper projecting at each end for the subsequent closing of the cartridge. One end of the tube is then closed and an extruded length of the gelatinous explosive Polar Saxonite (British Home Oflice permitted list) is inserted. The

.open end of the tube is then. closed and the cartridge is dipped in molten paraflin wax.

I claim:--

1. A blasting explosive cartridge including an inner core of explosive and an outer sheath comprising a mixture of at least one cooling salt and ammonium nitrate. 2. A blasting explosive cartridge including an inner core of explosiveland an outer sheath comprising a mixture of an alkali metal halide and ammonium nitrate. A

3. A -bla'sting explosive cartridge including an inner core of explosive and an outer sheath comprising a mixture of an alkali metal nitrate and ammonium nitrate. I

4. A blasting explosive cartridge including an inner core of explosive and an outer sheath comprising a mixture of ammonium perchlorate and at least one cooling salt.

5. A blasting explosive cartridge including an inner core of explosive and an outer sheath comprising a mixture of ammonium perchlorate, sodium nitrate and sodium chloride.

6. A blasting explosive cartridge including an inner core of explosive and an outer sheath comprising a mixture of ammonium nitrate, sodium chloride and ammonium dihydrogen phosphate.

'7. A blasting explosive cartridge including an inner core of explosive and an outer sheath comprising a mixture of at least one cooling salt, at least one power producing salt and a sensitizing explosive.

8. A blasting explosive cartridge including an inner core of explosive and an outer sheath com,- prising a mixture of at least one cooling salt, at least one power producing salt and an oxidizable carbonaceous material.

9. A blasting explosive cartridge including an inner core of explosive and an outer sheath comprising amixture of at least one cooling salt and at least one power-producing salt capable of undergoing explosive decomposition.

10. A blasting explosive cartridge including an inner core of explosive and an outer sheath extending over substantially the whole length of the core and around at least one end thereof and comprising a mixture of at least one cooling salt and at least one power-producing salt capable of undergoing explosive decomposition.

ALBERT GREVILLE WHITE. 

